Actually 500 and 501 status codes do not mean the box as such is offline

src/js/client.js

@@ -268,7 +268,7 @@ angular.module('Application').service('Client', ['$http', '$interval', '$timeout
                 // This means the box service is not reachable. We just show offline banner for now
             }
 
-            if (status >= 500) {
+            if (status >= 502) {
                 handleServerOffline();
                 return callback(new ClientError(status, data));
             }